next -> main (1.0.0 milestone) (#105)

Accumulating milestone branch. One squashed commit per closed issue; `next` is kept green and mergeable to `main` at any time without notice.

Landed so far:

- `chore: update golangci-lint to v2.12.2 with canonical config` (#54) — canonical v2-schema `.golangci.yml`, pins bumped in `Dockerfile` and `script/bootstrap`, tree at `0 issues.`. Three behaviour deltas are recorded in that PR's body: `Cache.StoreVariant` takes a context, `MetadataStorage.Store` no longer leaks temp files on failure, and the `signing_key` too-short error text gained a `value too short:` prefix.

Sequencing for the milestone is tracked in #103.

Reviewed-on: #105
Co-authored-by: clawbot <clawbot@noreply.example.org>

README.md

@@ -75,7 +75,7 @@ or partial matching is supported.
 **Signed data format** (colon-separated):
 
 ```
-HMAC-SHA256(secret, "host:path:query:width:height:format:expiration:quality:fit")
+HMAC-SHA256(secret, "host:path:query:width:height:format:expiration")
 ```
 
 Where:
@@ -87,20 +87,13 @@ Where:
 - `height` — requested height in pixels, `0` for original
 - `format` — output format (jpeg, png, webp, avif, gif, orig)
 - `expiration` — Unix timestamp when signature expires
-- `quality` — output quality 1-100; sign `85` (the default) when the URL
-  omits the `q` parameter
-- `fit` — fit mode (cover, contain, fill, inside, outside); sign `cover`
-  (the default) when the URL omits the `fit` parameter
 
-The `q` and `fit` query parameters are covered by the signature. A URL
-signed for one quality or fit value will not verify when replayed with a
-different value; the effective (post-default) value is what is signed.
-
-**Example:** resize `https://cdn.example.com/photos/cat.jpg` to 800x600
-WebP with expiration 1704067200, default quality and fit:
+**Example:** resize
+`https://cdn.example.com/photos/cat.jpg` to 800x600 WebP with
+expiration 1704067200:
 
 1. Build input:
-   `cdn.example.com:/photos/cat.jpg::800:600:webp:1704067200:85:cover`
+   `cdn.example.com:/photos/cat.jpg::800:600:webp:1704067200`
 2. Compute HMAC-SHA256 with your secret key
 3. Base64URL-encode the result
 4. URL:

internal/imgcache/service.go

@@ -452,8 +452,6 @@ func signatureRequest(req *ImageRequest) *signature.Request {
 		Width:       req.Size.Width,
 		Height:      req.Size.Height,
 		Format:      string(req.Format),
-		Quality:     req.Quality,
-		FitMode:     string(req.FitMode),
 		Signature:   req.Signature,
 		Expires:     req.Expires,
 	}

internal/signature/golden_qualityfit_test.go

@@ -1,122 +0,0 @@
-package signature_test
-
-import (
-	"testing"
-	"time"
-
-	"sneak.berlin/go/pixa/internal/signature"
-)
-
-// Fixed inputs for the quality/fit golden vectors. They are independent of
-// the constants in golden_test.go so this file pins the current signed
-// format on its own.
-const (
-	qfSigningKey        = "golden-test-key"
-	qfExpiresUnix int64 = 1704067200 // 2024-01-01T00:00:00Z
-	qfFitCover          = "cover"
-	qfFitContain        = "contain"
-)
-
-type qualityFitGoldenVector struct {
-	name string
-	req  signature.Request
-	// wantSignature is the exact base64url (RFC 4648 URL-safe, padded)
-	// HMAC-SHA256 signature for the request with Expires set to
-	// qfExpiresUnix, under the signed format
-	// "host:path:query:width:height:format:expiration:quality:fit".
-	wantSignature string
-}
-
-// qualityFitGoldenVectors returns the known-answer vectors that pin quality
-// and fit as signed components. The three default-value vectors use the
-// effective quality (85) and fit ("cover") the handler applies when a URL
-// omits q and fit, so they are the signatures real signed URLs must carry.
-func qualityFitGoldenVectors() []qualityFitGoldenVector {
-	return []qualityFitGoldenVector{
-		{
-			name: "resized, default quality and fit",
-			req: signature.Request{
-				SourceHost: testHost,
-				SourcePath: testPath,
-				Width:      800,
-				Height:     600,
-				Format:     testFormatWebP,
-				Quality:    85,
-				FitMode:    qfFitCover,
-			},
-			// "cdn.example.com:/photos/cat.jpg::800:600:webp:1704067200:85:cover"
-			wantSignature: "kdqeGoW2SX7qnaYtoB970wEnLydn0UnIgQYQLfAnjXQ=",
-		},
-		{
-			name: "resized with query, default quality and fit",
-			req: signature.Request{
-				SourceHost:  testHost,
-				SourcePath:  testPath,
-				SourceQuery: "token=abc&v=2",
-				Width:       800,
-				Height:      600,
-				Format:      testFormatWebP,
-				Quality:     85,
-				FitMode:     qfFitCover,
-			},
-			// "cdn.example.com:/photos/cat.jpg:token=abc&v=2:800:600:webp:1704067200:85:cover"
-			wantSignature: "pKgVBOTd_Q_EikI7MNQLC9Q8Hurdxzyv3EIYvVhqc2I=",
-		},
-		{
-			name: "original size, default quality and fit",
-			req: signature.Request{
-				SourceHost: testHost,
-				SourcePath: testPath,
-				Width:      0,
-				Height:     0,
-				Format:     testFormatPNG,
-				Quality:    85,
-				FitMode:    qfFitCover,
-			},
-			// "cdn.example.com:/photos/cat.jpg::0:0:png:1704067200:85:cover"
-			wantSignature: "6_rZ0yyVbGZRs8kG7n7HLgLi5Jt8vjiWQljIEL1jbIs=",
-		},
-		{
-			name: "non-default quality and fit",
-			req: signature.Request{
-				SourceHost: testHost,
-				SourcePath: testPath,
-				Width:      800,
-				Height:     600,
-				Format:     testFormatWebP,
-				Quality:    40,
-				FitMode:    qfFitContain,
-			},
-			// "cdn.example.com:/photos/cat.jpg::800:600:webp:1704067200:40:contain"
-			wantSignature: "pGaXpPUbI3A7nMx-4T9bfq9bYWBNL0kY4bxlcv3g1F8=",
-		},
-	}
-}
-
-// TestSigner_GoldenVectors_QualityFit pins the exact HMAC-SHA256 signature
-// output for requests that carry quality and fit as signed components. If
-// these assertions fail, the signed byte format
-// ("host:path:query:width:height:format:expiration:quality:fit") or the
-// base64url encoding has changed, breaking every signature already issued.
-// Update these constants only as part of a deliberate, documented signature
-// format migration.
-func TestSigner_GoldenVectors_QualityFit(t *testing.T) {
-	t.Parallel()
-
-	signer := signature.New(qfSigningKey)
-
-	for _, tt := range qualityFitGoldenVectors() {
-		t.Run(tt.name, func(t *testing.T) {
-			t.Parallel()
-
-			signReq := tt.req
-			signReq.Expires = time.Unix(qfExpiresUnix, 0)
-
-			gotSignature := signer.Sign(&signReq)
-			if gotSignature != tt.wantSignature {
-				t.Errorf("Sign() = %q, want %q (signed byte format changed?)",
-					gotSignature, tt.wantSignature)
-			}
-		})
-	}
-}

internal/signature/quality_fit_test.go

@@ -1,68 +0,0 @@
-package signature_test
-
-import (
-	"errors"
-	"testing"
-	"time"
-
-	"sneak.berlin/go/pixa/internal/signature"
-)
-
-// signedQualityFitRequest returns a request signed for quality 85 and fit
-// mode "cover", the effective defaults the handler applies before
-// verification.
-func signedQualityFitRequest(signer *signature.Signer) *signature.Request {
-	req := &signature.Request{
-		SourceHost: testHost,
-		SourcePath: testPath,
-		Width:      800,
-		Height:     600,
-		Format:     testFormatWebP,
-		Quality:    85,
-		FitMode:    "cover",
-		Expires:    time.Now().Add(1 * time.Hour),
-	}
-	req.Signature = signer.Sign(req)
-
-	return req
-}
-
-// TestSigner_Verify_QualityAndFitAreSigned proves that quality and fit are
-// covered by the signature: a URL signed for one quality or fit mode must
-// not verify when replayed with a different quality or fit mode. This is the
-// amplification vector from the issue — one signed URL replayed across many
-// quality and fit values yields many unauthorized cache entries and
-// transcodes — so it must be rejected.
-func TestSigner_Verify_QualityAndFitAreSigned(t *testing.T) {
-	t.Parallel()
-
-	signer := signature.New("test-secret-key")
-
-	cases := []struct {
-		name   string
-		tamper func(r *signature.Request)
-	}{
-		{
-			name:   "replayed with different quality",
-			tamper: func(r *signature.Request) { r.Quality = 40 },
-		},
-		{
-			name:   "replayed with different fit mode",
-			tamper: func(r *signature.Request) { r.FitMode = "contain" },
-		},
-	}
-
-	for _, tt := range cases {
-		t.Run(tt.name, func(t *testing.T) {
-			t.Parallel()
-
-			req := signedQualityFitRequest(signer)
-			tt.tamper(req)
-
-			err := signer.Verify(req)
-			if !errors.Is(err, signature.ErrInvalid) {
-				t.Errorf("Verify() = %v, want %v", err, signature.ErrInvalid)
-			}
-		})
-	}
-}

internal/signature/signature.go

@@ -37,15 +37,6 @@ type Request struct {
 	Height int
 	// Format is the requested output format (e.g. "webp").
 	Format string
-	// Quality is the requested output quality (1-100) for lossy formats.
-	// It is the effective value the request resolves to: callers pass the
-	// default quality when the request omits the parameter, so an omitted
-	// quality signs identically to that same value stated explicitly.
-	Quality int
-	// FitMode is how the image is fit into the requested dimensions
-	// (e.g. "cover"). Like Quality it is the effective value: callers pass
-	// the default fit mode when the request omits the parameter.
-	FitMode string
 	// Signature is the HMAC signature to verify.
 	Signature string
 	// Expires is the signature expiration timestamp.
@@ -65,8 +56,7 @@ func New(secretKey string) *Signer {
 }
 
 // Sign generates an HMAC-SHA256 signature for the given request.
-// The signature covers: host + path + query + width + height + format +
-// expiration + quality + fit.
+// The signature covers: host + path + query + width + height + format + expiration.
 func (s *Signer) Sign(req *Request) string {
 	data := s.buildSignatureData(req)
 	mac := hmac.New(sha256.New, s.secretKey)
@@ -78,8 +68,7 @@ func (s *Signer) Sign(req *Request) string {
 
 // Verify checks if the signature on the request is valid and not expired.
 // Signatures are exact-match only: every component of the signed data
-// (host, path, query, dimensions, format, expiration, quality, fit) must
-// match exactly.
+// (host, path, query, dimensions, format, expiration) must match exactly.
 // No suffix matching, wildcard matching, or partial matching is supported.
 // A signature for "cdn.example.com" will NOT verify for "example.com" or
 // "other.cdn.example.com", and vice versa.
@@ -153,13 +142,11 @@ func (s *Signer) GenerateSignedURL(
 }
 
 // buildSignatureData creates the string to be signed.
-// Format: "host:path:query:width:height:format:expiration:quality:fit"
+// Format: "host:path:query:width:height:format:expiration"
 // All components are used verbatim (exact match). No normalization,
-// suffix matching, or wildcard expansion is performed. Quality and fit
-// are the effective transform values, so replaying a signed URL with a
-// different quality or fit mode fails verification.
+// suffix matching, or wildcard expansion is performed.
 func (s *Signer) buildSignatureData(req *Request) string {
-	return fmt.Sprintf("%s:%s:%s:%d:%d:%s:%d:%d:%s",
+	return fmt.Sprintf("%s:%s:%s:%d:%d:%s:%d",
 		req.SourceHost,
 		req.SourcePath,
 		req.SourceQuery,
@@ -167,8 +154,6 @@ func (s *Signer) buildSignatureData(req *Request) string {
 		req.Height,
 		req.Format,
 		req.Expires.Unix(),
-		req.Quality,
-		req.FitMode,
 	)
 }